Light valves used in displays or in smart windows are typically limited to electronic switching between two states, typically a clear and a black state. For full-color operation, color filters are utilized which typically reduce the optical transmission or reflection by three times. Furthermore, even the clear to opaque switching mechanism can be inefficient itself, further limiting the optical performance to the point of preventing commercial success for applications such as smart windows.
Smart windows are essentially laminates having light transmission or reflectance properties which can be modified. Although smart windows are most often created using laminate approaches, the layer which modifies light transmission or reflection properties can also be sandwiched between two plates of more rigid glass. The modification of the reflectance or transmission characteristics of the laminate can be caused by physical, electrical or other stimulus. More specifically, smart glass is glass or a glazing whose light transmission properties are altered when voltage, light or heat is applied. There are various smart glass technologies, including electrochromic, photochromic, thermochromic, suspended particle, microblind and polymer dispersed liquid crystal devices.
When installed in the envelope of buildings, smart glass creates climate-adaptive building shells with the ability to save costs for heating, air conditioning and lighting, and avoid the cost of installing and maintaining motorized light screens or blinds or curtains. Most smart glass blocks ultraviolet light, reducing fabric fading. Smart glass has limited applications due to the high cost of manufacture and the limitations with respect to altering light transmission.
Typical methods of forming smart glass are extremely expensive. Further, most smart glass merely changes from transparent to translucent and is monochromal. Therefore, mechanical blinds or screens can basically achieve the same results as smart glass at a significantly-reduced price. For this reason, there is relatively little motivation to install smart glass in buildings.